Quick disconnect-type couplings are used, for example, to connect hoses in hydraulic fluid lines. A typical application is on agricultural tractors to connect the tractor hydraulic system with attachable implements. The tractor typically includes one or more female coupler sockets, while the implements include one or more male coupler nipples. Pneumatic and other applications for such couplings are also well known.
Over the years changes have occurred in these systems which have required changes and performance improvements in the couplings. One early coupling design is shown in U.S. Pat. No. 4,077,433 where the female coupler includes a valve body slideable within the housing and a poppet valve internal to the valve body. The poppet valve is axially movable to engage a check valve in a male coupler when the male coupler is inserted into the female coupler. When low pressure is present in the male coupler, the poppet valve moves the check valve (ball valve) off its valve seat to allow flow from the female coupler to pass to the male coupler. When higher pressures are present in the male coupler, an internal passage in the poppet valve provides incoming fluid pressure to the rear surface of the poppet valve. Due to the differences in effective surface areas, the fluid pressure assists in driving the poppet valve against the check valve to move the check valve into an open position.
An improvement in this coupling is shown in U.S. Pat. No. 4,598,896, where a separate piston is located around the poppet valve. The piston can engage the poppet valve when moved forwardly. An internal passage in the poppet valve provides fluid pressure to the rear surface of the piston, which assists in driving the poppet valve against the check valve in the male coupler in high pressure situations. A spool is also provided around the piston and poppet valve in this coupling. The spool is fixed to the valve body and includes a port for exhausting pressure within the poppet valve. A retainer sleeve with a seal surrounds the port on the spool, and when the valve body slides within the housing (when the male coupler is inserted or removed), the port relieves the internal pressure in the female coupler to atmosphere.
In some cases, particularly when a pair of couplers are used to direct fluid to and from a hydraulic cylinder in an implement, a check valve mechanism is also provided in the female coupler to prevent the rapid backflow of pressure out of the female coupler when a pressure imbalance occurs within the system, such as during thermal expansion of the fluid caused by severe operating conditions, or when the implement is dragged over an uneven surface. In these situations, one of the female couplers can allow the check valve in an associated male coupler to close, which can cause a block in the system when the flow through the female coupler is desired.
To remedy this problem, some female couplers include a check valve mechanism which allows fluid to flow relatively unimpeded rearwardly to the rear surface of the piston, but which restricts or prevents fluid flow forwardly out of the female coupler. One known check valve mechanism includes a valve ball located within the internal bore of the piston which is spring-biased in both directions to allow fluid to flow rearwardly through the piston at a higher flow rate than forwardly through the piston.
The above couplings have received wide-spread acceptance in the marketplace for providing reliable, serviceable and effective components which operate under a variety of conditions. However, some of these couplings direct the fluid internally through the poppet valve to the rear surface of the piston. The flow path includes a radial hole formed in the side of the poppet valve, and a central bore extending axially through the poppet valve. A spring is commonly disposed within the central bore of the poppet valve for biasing the poppet valve against the valve seat. As the spring flexes, the spring can interfere with the flow through the radial hole, which can reduce or even temporarily interrupt the flow through the poppet valve. This can cause an uneven driving force of the piston against the poppet valve, which can be undesirable in certain applications.
Other of these couplings have the disadvantage that the check valve mechanism is complicated, can be time-consuming to assemble, and can require inspection and frequent repair or replacement if necessary to maintain consistent operation.
In any case, it is believed that there is a constant demand in the industry for novel and unique couplings which are reliable, easily serviceable, and operate under a variety of conditions.